BOPP heat-seal film By employing a unique manufacturing process, an ultra-thin layer of metallic aluminum is deposited onto the surface of plastic film, creating a composite flexible packaging material. The most common production method is aluminum vapor deposition: a high‑vacuum pump is used to evaporate metallic aluminum at elevated temperatures, allowing the aluminum vapor to condense and form a thin metallic coating on the plastic film’s surface. This gives BOPP heat‑seal films a metallic appearance. Now, let’s explore the key characteristics of the BOPP heat‑seal film manufacturing process.

　　BOPP heat-seal film, with its unique characteristics and metallic finish, is an economical yet high‑quality packaging solution that offers excellent performance and versatile applications. It is widely used for vacuum preservation of flavored foods, marinated products, and agricultural goods, as well as for the outer packaging of pharmaceuticals, skincare products, and tea. Additionally, BOPP heat-seal film is frequently employed in packaging printing as a substrate for gold‑foil lettering and logo markings.

　　Characteristics of BOPP heat-seal film:

　　1. Made with 99.99% high‑quality aluminum wire, the aluminum layer is uniform and highly dense, providing excellent barrier properties. It effectively blocks steam, water vapor, and odors, extending the shelf life of the outer packaging and preserving the flavor of perishable foods, thereby enhancing the performance of aluminum foil bags to a certain extent.

　　2. It boasts an excellent metallic finish, with a light transmittance of up to 97%, blocks light, filters ultraviolet rays, and helps keep the outer packaging fresh.

　　3. The aluminum‑coated layer exhibits excellent electrical conductivity, effectively dissipating static electricity. Particularly for powdered products, environmental contamination can make sealing the package challenging; however, this coating ensures a wide heat‑seal zone and high heat‑seal strength, thereby guaranteeing the integrity of the outer packaging’s seal.

　　4. It exhibits a long discharge voltage plateau and maintains strong surface support for an extended period, demonstrating excellent compatibility with downstream manufacturing processes such as packaging printing, lamination, and multi‑functional electroplating.

　　BOPP heat-seal film, produced via biaxial stretching, exhibits excellent and very high tensile strength and impact resistance, along with outstanding transparency. Consequently, it is a widely used printing substrate in the packaging industry. However, its heat-sealing performance is poor, making it unsuitable as the heat-seal layer in composite films. With a high melting point exceeding 160°C, it offers good high-temperature resistance; yet, due to polypropylene’s relatively high glass transition temperature, it generally also demonstrates good low-temperature resistance. BOPP heat-seal film provides moderate barrier properties, particularly against water vapor, but its oxygen-barrier performance is limited. When used as a composite base material, it typically has a thickness of around 20 microns, and for most applications where barrier requirements are not stringent, BOPP heat-seal film can be selected as the printing and lamination substrate.

　　BOPP heat-seal film biaxial stretching is a technology developed to achieve subsequent or simultaneous orientation of thermoplastic materials. At present, there are two main production technologies for BOPP heat-seal film:

　　1. Tubular membrane method.

　　2. Flat-membrane method.

　　It is divided into segmented biaxial stretching and synchronous biaxial stretching. Products obtained through the flat‑film method, which involves simultaneous biaxial stretching, exhibit the advantage of isotropic properties; however, the equipment is complex, manufacturing is challenging, and costs are high, so this approach has not been widely adopted. Biaxial stretching is currently the method favored by many manufacturers, but the resulting products show longitudinal–transverse variations in properties such as tensile strength, elongation at break, and thermal shrinkage—though these differences have only a minor impact on overall product quality. Nevertheless, this method offers advantages such as high throughput, fast processing speeds, wide web widths, and stable product quality.